<PAGE>   1
                                                                     EXHIBIT 4.6


               THIRD AMENDMENT TO FIRST RESTATED CREDIT AGREEMENT

         THIS THIRD AMENDMENT TO FIRST RESTATED CREDIT AGREEMENT (this
"Amendment") made as of the 30th day of October, 1996, by and among TPC
Corporation, a Delaware corporation ("Borrower"), Internationale Nederlanden
(U.S.) Capital Corporation ("ING Capital"), as Agent ("Agent"), CIBC Inc., as
Co-Agent ("Co-Agent") and the Lenders under the Credit Agreement ("Lenders"),

                              W I T N E S S E T H:

         WHEREAS, Borrower, Agent, Co-Agent and Lenders entered into that
certain First Restated Credit Agreement dated as of September 25, 1995, as
amended by that certain First Amendment to First Restated Credit Agreement,
effective as of September 25, 1995, and that certain Second Amendment to First
Restated Credit Agreement dated as of December 28, 1995 (as amended, the
"Original Agreement") for the purpose and consideration therein expressed,
whereby ING Capital and CIBC Inc. became obligated to make Loans and have made
Loans to Borrower as therein provided; and

         WHEREAS, Borrower, Agent, Co-Agent and Lenders desire to amend the
Original Agreement (i) to increase the Commitment, and (ii) for the other
purposes set forth herein;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements contained herein and in the Original Agreement and in
consideration of the Loans which may hereafter be made by Lenders to Borrower,
and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, the parties hereto do hereby agree as follows:

                    ARTICLE I. -- Definitions and References

         Section 1.1. Terms Defined in the Original Agreement. Unless the
context otherwise requires or unless otherwise expressly defined herein, the
terms defined in the Original Agreement shall have the same meanings whenever
used in this Amendment.

         Section 1.2. Other Defined Terms. Unless the context otherwise
requires, the following terms when used in this Amendment shall have the
meanings assigned to them in this Section 1.2.

                  "Amendment" shall mean this Third Amendment to First Restated 
         Credit Agreement.

                  "Amendment Documents" means this Amendment and the Renewal 
         Notes.

                  "Credit Agreement" means the Original Agreement as amended 
         hereby.

                  "Effective Date" has the meaning given it in Section 3.1.

                  "Original Notes" means the "Notes" referred to and defined as 
         such in the Original Agreement.

                  "Renewal Notes" has the meaning given it in Section 3.1(ii).





                                       1
<PAGE>   2



                ARTICLE II. -- Amendments to Original Agreement

         Section 2.1. Defined Terms. The definitions of "Borrowing Base",
"Borrowing Base Report", "Eligible Inventory" and "Eligible Receivables" in
Section 1.1 of the Original Agreement are hereby deleted.

         The definitions of "Borrower", "Commitment", "Commitment Termination
Date" and "Required Hedges" in Section 1.1 of the Original Agreement are hereby
amended in their entirety to read as follows:

                  "Borrower" means TPC Corporation (f/k/a Tejas Power 
         Corporation), a Delaware corporation.

                  "Commitment" means the amount of $40,000,000.

                  "Commitment Termination Date" means January 1, 1999,
         provided, Borrower may, by written request to Agent, Co-Agent and each
         Lender at any time not less than thirty days prior to the Commitment
         Termination Date (whether the initial Commitment Termination Date or
         such date as previously extended by Lenders in their sole discretion
         pursuant to this proviso), request Lenders to extend the Commitment
         Termination Date upon the same terms and conditions as set forth
         herein, and Lenders may, in their individual sole discretion and upon
         their unanimous agreement, extend the Commitment Termination Date for
         a period of up to one year.

                  "Required Hedges" means for each Fiscal Quarter listed below,
         forward, future, swap or hedging contracts, with a Hedging Rate capped
         at eight percent (8%) per annum, entered into by Borrower pursuant to
         Section 5.2(p)(ii), in an aggregate notional amount not less than the
         amount listed below for each such Fiscal Quarter:
<TABLE>
<CAPTION>

         Fiscal Quarter                                       Hedged Amount of Indebtedness
         --------------                                       -----------------------------
<S>                                                                    <C>        
         July 1, 1996 to September 30, 1996                            $38,500,000
           (commencing August 19, 1996)
         October 1, 1996 to December 31, 1996                          $36,500,000
         January 1, 1997 to March 31, 1997                             $34,500,000
         April 1, 1997 to June 30, 1997                                $32,500,000
         July 1, 1997 to September 30, 1997                            $30,500,000
         October 1, 1997 to December 31, 1997                          $29,500,000
         January 1, 1998 to March 31, 1998                             $28,500,000
         April 1, 1998 to June 30, 1998                                $27,500,000
         July 1, 1998 to September 30, 1998                            $26,500,000
         October 1, 1998 to December 31, 1998                          $25,500,000
</TABLE>

         For purposes of this definition, "Hedging Rate" means the rate per
         annum reported on each day on Telerate Access Service Page 3750
         (British Bankers Association Settlement Rate) as the London Interbank
         Offered Rate for dollar deposits having a three-month term and in an
         amount of $1,000,000 or more (or, if such Page shall cease to be
         publicly available or if the information contained on such Page, in
         Agent's sole judgment, shall cease to accurately reflect such London
         Interbank 





                                       2
<PAGE>   3


         Offered Rate, such rate as reported by any publicly available source
         of similar market data selected by Agent that, in Agent's sole
         judgment, accurately reflects such London Interbank Offered Rate).

         Section 2.2. Deletion of Borrowing Base Provisions. The following
references to "Borrowing Base" are hereby amended to refer instead to
"Commitment":

         Clause (b) of the first sentence of Section 2.1 of the Original
         Agreement; Second sentence of Section 2.1 of the Original Agreement;
         First sentence of Section 2.2(b) of the Original Agreement; Last
         sentence of Section 2.2(b) of the Original Agreement; First sentence
         of Section 2.7(a) of the Original Agreement; Clause (i) of the first
         sentence of Section 2.9 of the Original Agreement; and Section 2.9(e).

         Sections 2.28, 2.29 and 5.1(b)(vii) of the Original Agreement are
hereby deleted.

         Section 2.3. Requests for Advances. The first sentence of Section 
2.2(a) of the Original Agreement is hereby amended in its entirety to read as 
follows:

         Borrower must give to Agent written notice, or telephonic notice
         promptly confirmed in writing, of any requested Advances, which notice
         must be received by Agent not later than 11:00 a.m., New York, New
         York time, on the date of the requested Advances (or three Business
         Days prior to the date of the requested Advances if Borrower is
         desires for all or any part of such Advances to make up a Tranche of
         LIBOR Rate Portions on such date).

         Section 2.4. Mandatory Prepayments. Section 2.7(b) of the Original
Agreement is hereby deleted.

         Section 2.5. Letters of Credit. The first sentence of Section 2.11 of 
the Original Agreement is hereby amended in its entirety to read as follows:

         Letters of Credit shall be issued solely for Borrower's general
         corporate purposes, including without limitation for margin call
         purposes relating to forward, future, swap or hedging contracts as
         permitted by Section 5.2(p).


                                       3

<PAGE>   4



         Section 2.6. Limitation on Credit Extensions. Section 5.2(h) of the
Original Agreement is hereby amended by adding a new clause (v) at the end
thereof, to read as follows:

         (v) other extensions of credit, advances or loans, so long as the
     aggregate amount of such extensions of credit, advances and loans made by
     Borrower and all Restricted Subsidiaries does not exceed $1,000,000.

         Section 2.7. EBITAD. Section 5.2(o)(ii) of the Original Agreement is
hereby amended in its entirety to read as follows:

         (ii) The ratio of (A) Borrower's and Restricted Subsidiaries' EBITAD
     to (B) the sum of Debt Service plus scheduled payments of principal
     (including the principal component of rentals or capitalized leases) on
     Restricted Debt plus $1,000,000 maintenance capital expenditures for each
     four-Fiscal Quarter period will not be less than (1) 1.10 to 1 for the
     four-Fiscal Quarter period ending December 31, 1996; (2) 1.15 to 1 for the
     four-Fiscal Quarter periods ending on each of March 31, 1997, June 30,
     1997, September 30, 1997 and December 31, 1997; and (3) 1.20 to 1 for the
     four-Fiscal Quarter period ending March 31, 1998 and each four-Fiscal
     Quarter period thereafter.

         Section 2.8. Name Change of Borrower. As of May 6, 1996, Borrower
changed its name from Tejas Power Corporation to TPC Corporation. All
references to "Borrower" in any Loan Document shall as of such date and
thereafter refer to "TPC Corporation, a Delaware corporation".

         Section 2.9. Consent and Waiver re: Prism; Limited Waiver of EBITAD.
Agent, Co-Agent and Lenders hereby (i) consent to the extension of credit by
Borrower to PRISM Information I, LLC in the amount of $380,000, as evidenced by
a promissory note dated September 13, 1996, secured by certain collateral and
maturing on September 13, 1998, and (ii) waive Borrower's breach of Section
5.2(h) of the Credit Agreement thereby and any related Default or Event of
Default under Section 7.1(c) of the Credit Agreement. Agent, Co-Agent and
Lenders hereby waive (i) Borrower's breach of Section 5.2(o) of the Credit
Agreement for the Fiscal Quarter ending September 30, 1996 and (ii) any related
Default or Event of Default under Section 7.1(c) of the Credit AgreemeAgent,
Co-Agent and Lenders hereby waive (a) Borrower's failure to maintain the
Required Hedges, as set forth in Section 5.1(l) of the Credit Agreement, prior
to the date hereof and (b) any related Default or Event of Default under
Section 7.1(c) of the Credit Agreement.

         Section 2.10. Exhibits. Exhibits A and B to the Original Agreement are
hereby amended in their entirety to read as set forth in Exhibits A and B
attached hereto. Exhibit H to the Original Agreement is hereby deleted.

                  ARTICLE III. -- Conditions of Effectiveness

         Section 3.1. Effective Date. This Amendment shall become effective as 
of the date first above written (the "Effective Date") when, and only when, (i)
Agent shall have


                                       4

<PAGE>   5



received, at Agent's office, a counterpart of this Amendment executed and
delivered by Borrower and each Lender, (ii) Borrower shall have issued and
delivered to Agent, for subsequent delivery to each Lender, a Note with
appropriate insertions in the form attached hereto as Exhibit A payable to the
order of such Lender on or before January 1, 1999 (the "Renewal Notes"), duly
executed on behalf of Borrower, dated the date hereof, and in a principal
amount equal to such Lender's Percentage Share, set forth opposite such
Lender's name on the signature pages hereto, of the Commitment, and (iii) Agent
shall have additionally received all of the following documents, each document
(unless otherwise indicated) being dated the date of receipt thereof by Agent,
duly authorized, executed and delivered, and in form and substance satisfactory
to Agent:

                  (a) Opinion of Counsel for Borrower. Agent shall have
         received (i) the written opinion of M. Scott Jones, Esq., general
         counsel of Borrower, dated as of the date of this Amendment, addressed
         to Agent, Co-Agent and Lenders, substantially in the form of that
         certain opinion dated September 25, 1995 by M. Scott Jones, Esq. to
         Agent and Lenders, to the effect that, among other things, this
         Amendment and each Renewal Note have been duly authorized, executed
         and delivered by Borrower, and (ii) the written opinion of Baker &
         Botts, L.L.P., special New York counsel to Borrower, dated as of the
         date of this Amendment, addressed to Agent, Co-Agent and Lenders,
         substantially in the form of that certain opinion dated September 25,
         1995 by Baker & Botts, L.L.P. to Agent and Lenders, to the effect
         that, among other things, the Credit Agreement and each Renewal Note
         constitute the legal, valid and binding obligations of Borrower,
         enforceable in accordance with their terms (subject, as to enforcement
         of remedies, to applicable bankruptcy, reorganization, insolvency and
         similar laws and to moratorium laws and other laws affecting
         creditors' rights generally from time to time in effect).

                  (b) Officer's Certificate. Agent shall have received a
         certificate of a duly authorized officer of Borrower to the effect
         that all of the representations and warranties set forth in Article IV
         hereof are true and correct at and as of the time of such
         effectiveness.

                  (c) Supporting Documents. Agent shall have received (i) a
         certificate of the Secretary of Borrower dated the date of this
         Amendment certifying that attached thereto is a true and complete copy
         of resolutions adopted by the Board of Directors of Borrower
         authorizing the execution, delivery and performance of this Amendment
         and each Renewal Note and certifying the names and true signatures of
         the officers of Borrower authorized to sign this Amendment and each
         Renewal Note, and (ii) such supporting documents as Agent may
         reasonably request.

                 ARTICLE IV. -- Representations and Warranties

         Section 4.1. Representations and Warranties of Borrower. In order to
induce each Lender to enter into this Amendment, Borrower represents and
warrants to Agent, Co-Agent and each Lender that:

               (a) The representations and warranties contained in Section 4.1
          of the Original Agreement are true and correct at and as of the
          Effective Date.



                                       5

<PAGE>   6

                  (b) Borrower is duly authorized to execute and deliver this
         Amendment and each Renewal Note and is and will continue to be duly
         authorized to borrow monies and to perform its obligations under the
         Credit Agreement. Borrower has duly taken all corporate action
         necessary to authorize the execution and delivery of this Amendment
         and each Renewal Note and to authorize the performance of the
         obligations of Borrower hereunder and thereunder.

                  (c) The execution and delivery by Borrower of this Amendment
         and each Renewal Note, the performance by Borrower of its obligations
         hereunder and thereunder and the consummation of the transactions
         contemplated hereby and thereby do not and will not conflict with any
         provision of law, statute, rule or regulation or of the certificate of
         incorporation and bylaws of Borrower, or of any material agreement,
         judgment, license, order or permit applicable to or binding upon
         Borrower, or result in the creation of any lien, charge or encumbrance
         upon any assets or properties of Borrower. Except for those which have
         been obtained, no consent, approval, authorization or order of any
         court or governmental authority or third party is required in
         connection with the execution and delivery by Borrower of this
         Amendment and each Renewal Note or to consummate the transactions
         contemplated hereby and thereby.

                  (d) When duly executed and delivered, each of this Amendment,
         the Credit Agreement and the Renewal Notes will be a legal and binding
         obligation of Borrower, enforceable in accordance with its terms,
         except as limited by bankruptcy, insolvency or similar laws of general
         application relating to the enforcement of creditors' rights and by
         equitable principles of general application.

                  (e) The audited annual Consolidated financial statements of
         Borrower dated as of December 31, 1995 and the unaudited quarterly
         Consolidated financial statements of Borrower dated as of June 30,
         1996 fairly present the Consolidated financial position at such dates
         and the Consolidated statement of operations and the changes in
         Consolidated financial position for the periods ending on such dates
         for Borrower. Copies of such financial statements have heretofore been
         delivered to Agent, Co-Agent and each Lender. Since December 31, 1995,
         no material adverse change has occurred in the financial condition or
         businesses or in the Consolidated financial condition or businesses of
         Borrower.

                          ARTICLE V. -- Miscellaneous

         Section 5.1. Ratification of Agreements. The Original Agreement as
hereby amended is hereby ratified and confirmed in all respects. Any reference
to the Credit Agreement in any Loan Document shall be deemed to be a reference
to the Original Agreement as hereby amended. Any reference to the Notes in any
other Loan Document shall be deemed to be a reference to the Renewal Notes
issued and delivered pursuant to this Amendment. The execution, delivery and
effectiveness of this Amendment and the Renewal Notes shall not, except as
expressly provided herein or therein, operate as a waiver of any right, power
or remedy of Lenders under the Credit Agreement, the Notes, or any other Loan
Document nor constitute a waiver of any provision of the Credit Agreement, the
Notes or any other Loan Document.



                                       6

<PAGE>   7

         Section 5.2. Survival of Agreements. All representations, warranties,
covenants and agreements of Borrower herein shall survive the execution and
delivery of this Amendment and the performance hereof, including without
limitation the making or granting of the Loans and the issuance and delivery of
the Renewal Notes, and shall further survive until all of the Obligations are
paid in full. All statements and agreements contained in any certificate or
instrument delivered by any Related Person hereunder or under the Credit
Agreement to any Lender shall be deemed to constitute representations and
warranties by, and/or agreements and covenants of, Borrower under this
Amendment and under the Credit Agreement.

         Section 5.3. Delivery of Original Notes. Each Lender shall promptly
deliver to Agent, for subsequent delivery to Borrower, the Original Note
heretofore delivered to it under the Original Agreement.

         Section 5.4. Loan Documents. This Amendment and each Renewal Note are 
each a Loan Document, and all provisions in the Credit Agreement pertaining to
Loan Documents apply hereto and thereto.

         Section 5.5. Governing Law. This Amendment shall be governed by and
construed in accordance the laws of the State of New York and any applicable
laws of the United States of America in all respects, including construction,
validity and performance.

         Section 5.6. Counterparts. This Amendment may be separately executed
in counterparts and by the different parties hereto in separate counterparts,
each of which when so executed shall be deemed to constitute one and the same
Amendment.


                                      7

<PAGE>   8



         IN WITNESS WHEREOF, this Amendment is executed as of the date first
above written.

<TABLE>
<S>                                   <C>
                                      TPC CORPORATION
                             
                             
                                      By:   /s/   Robert D. Kincaid
                                            -------------------------------------------
                                            Robert D. Kincaid, Treasurer
                             
                             
Percentage Share                      INTERNATIONALE NEDERLANDEN (U.S.)
                                      CAPITAL CORPORATION, as Agent and a
      50%                             Lender
                             
                             
                                      By:   /s/   Trond O. Rokholt
                                            -------------------------------------------
                                            Trond O. Rokholt, Senior Vice President
                             
                             
Percentage Share                      CIBC INC., as Co-Agent, Issuing Bank and a Lender
                             
      50%                    
                                      By:   /s/   Robert E. Long
                                            -------------------------------------------
                                            Name:     Robert E. Long
                                            Title:    Managing Director
                             
                                      Address:
                             
                                      2 Houston Center, Suite 1200
                                      900 Fannin Street
                                      Houston, Texas  77010
                                      Attention:  Mr. Robert Long
                                      Phone:  (713) 658-8400
                                      Fax:  (713) 658-9922
                             
                                      with a copy to:
                             
                                      Canadian Imperial Bank of Commerce
                                      Two Paces West
                                      2727 Paces Ferry Road, Suite 1200
                                      Atlanta, Georgia  30339
                                      Attention:  Ms. Joan Moseley
                                      Phone:  (770) 319-4828
                                      Fax:  (770) 319-4950
                             

</TABLE>

                                      8

<PAGE>   9
                                                                       EXHIBIT A


                                PROMISSORY NOTE


20,000,000                    New York, New York              October 30, 1996

         FOR VALUE RECEIVED, the undersigned, TPC Corporation, a Delaware
corporation (herein called "Borrower"), hereby promises to pay to the order of
____________________________________________ (herein called "Lender"), the
principal sum of TWENTY MILLION AND NO/100 DOLLARS ($20,000,000), or, if
greater or less, the aggregate unpaid principal amount of the Loan made under
this Note by Lender to Borrower pursuant to the terms of the Credit Agreement
(as hereinafter defined), together with interest on the unpaid principal
balance thereof as hereinafter set forth, both principal and interest payable
as herein provided in lawful money of the United States of America at the
offices of Lender, 135 East 57th Street, New York, New York or at such other
place within New York County, New York, as from time to time may be designated
by the holder of this Note.

         This Note (a) is issued and delivered under that certain First
Restated Credit Agreement dated September 25, 1995 among Borrower,
Internationale Nederlanden (U.S.) Capital Corporation, as Agent, and the
lenders named therein (herein, as from time to time supplemented, amended or
restated, called the "Credit Agreement"), and is a Note as defined therein, and
(b) is subject to the terms and provisions of the Credit Agreement, which
contains provisions for payments and prepayments hereunder and acceleration of
the maturity hereof upon the happening of certain stated events. Payments on
this Note shall be made and applied as provided herein and in the Credit
Agreement. Reference is hereby made to the Credit Agreement for a description
of certain rights, limitations of rights, obligations and duties of the parties
hereto and for the meanings assigned to terms used and not defined herein.

         For the purposes of this Note, the following terms have the meanings
assigned to them below:

                  "Maximum Rate" means at the particular time in question the
         maximum rate of interest which, under applicable law, may then be
         charged on this Note. If such maximum rate of interest changes after
         the date hereof, the Maximum Rate shall be automatically increased or
         decreased, as the case may be, without notice to Borrower from time to
         time as of the effective time of each change in such maximum rate. If
         applicable law ceases to provide for such a maximum rate of interest,
         the Maximum Rate shall be a per annum rate of interest equal to
         twenty-five percent (25.0%) plus the Base Rate from time to time in
         effect.

                  "Base Rate Payment Date" means (i) the last day of each
         March, June, September and December of each year, beginning December
         31, 1996, and (ii) any day on which past due interest or principal is
         owed hereunder and is unpaid. If the terms hereof or of the Credit
         Agreement provide that payments of interest or  



                                      1

<PAGE>   10

          principal hereon shall be deferred from one Base Rate Payment Date to
          another day, such other day shall also be a Base Rate Payment Date.

                  "LIBOR Rate Payment Date" means, with respect to any LIBOR
         Rate Portion: (i) the day on which the related Interest Period ends
         (and, if such Interest Period is longer than three months, the
         three-month anniversary of the first day of such Interest Period), and
         (ii) any day on which past due interest or past due principal is owed
         hereunder with respect to such LIBOR Rate Portion and is unpaid. If
         the terms hereof or of the Credit Agreement provide that payments of
         interest or principal with respect to such LIBOR Rate Portion shall be
         deferred from one LIBOR Rate Payment Date to another day, such other
         day shall also be a LIBOR Rate Payment Date.

         The principal amount of this Note, together with all unpaid accrued
interest hereon, shall be due and payable in full on January 1, 1999.

         The Base Rate Portion of the Loan (exclusive of any past due principal
or interest) from time to time outstanding shall bear interest on each day
outstanding at the Base Rate in effect on such day. On each Base Rate Payment
Date Borrower shall pay to the holder hereof all unpaid interest which has
accrued on the Base Rate Portion to but not including such Base Rate Payment
Date. Each LIBOR Rate Portion of the Loan (exclusive of any past due principal
or interest) shall bear interest on each day during the related Interest Period
at the related LIBOR Rate in effect on such day. On each LIBOR Rate Payment
Date relating to such LIBOR Rate Portion Borrower shall pay to the holder
hereof all unpaid interest which has accrued on such LIBOR Rate Portion to but
not including such LIBOR Rate Payment Date. All past due principal and past due
interest owed under this Note shall bear interest on each day outstanding at
the Late Payment Rate in effect on such day, and such interest shall be due and
payable daily as it accrues. Notwithstanding the foregoing provisions of this
paragraph, if at any time the rate at which interest is payable on this Note
(considering together all portions of the Loan and the interest payable
thereon) exceeds the Maximum Rate, this Note shall bear interest at the Maximum
Rate only but shall continue to bear interest at the Maximum Rate until such
time as the total amount of interest accrued hereon equals (but does not
exceed) the total amount of interest which would have accrued hereon had there
been no Maximum Rate applicable hereto.

         Notwithstanding the foregoing paragraph and all other provisions of
this Note, in no event shall the interest payable hereon, whether before or
after maturity, exceed the maximum interest which, under applicable law, may be
charged on this Note, and this Note is expressly made subject to the provisions
of the Credit Agreement which more fully set out the limitations on how
interest accrues hereon.

         If this Note is placed in the hands of an attorney for collection
after default, or if all or any part of the indebtedness represented hereby is
proved, established or collected in any court or in any bankruptcy,
receivership, debtor relief, probate or other court proceedings, Borrower and
all endorsers, sureties and guarantors of this Note jointly and severally agree
to pay reasonable attorneys' fees and collection costs to the holder hereof in
addition to the principal and interest payable hereunder.



                                       2

<PAGE>   11

         Borrower and all endorsers, sureties and guarantors of this Note
hereby severally waive demand, presentment, notice of demand and of dishonor
and nonpayment of this Note, protest, notice of protest, notice of intention to
accelerate the maturity of this Note, declaration or notice of acceleration of
the maturity of this Note, diligence in collecting, the bringing of any suit
against any party and any notice of or defense on account of any extensions,
renewals, partial payments or changes in any manner of or in this Note or in
any of its terms, provisions and covenants, or any releases or substitutions of
any security, or any delay, indulgence or other act of any trustee or any
holder hereof, whether before or after maturity.

         THIS NOTE AND THE RIGHTS AND DUTIES OF THE PARTIES HERETO SHALL BE
GOVERNED BY THE LAWS OF THE STATE OF NEW YORK (WITHOUT REGARD TO PRINCIPLES OF
CONFLICTS OF LAW), EXCEPT TO THE EXTENT THE SAME ARE GOVERNED BY APPLICABLE
FEDERAL LAW.

                    This Note is given in  renewal,  extension  and  increase,
but not in novation or extinguishment, of that certain Promissory Note dated
December 28, 1995 by Borrower in the aggregate original principal amount of
$15,000,000, payable to the order of Lender.

                                              TPC CORPORATION


                                              By:
                                                 ----------------------------
                                                 Robert D. Kincaid, Treasurer



                                       3

<PAGE>   12
                                                                      EXHIBIT B


                              REQUEST FOR ADVANCES

         Reference is made to that certain First Restated Credit Agreement
dated as of September 25, 1995 (as from time to time amended, the "Agreement"),
by and among TPC Corporation ("Borrower"), Internationale Nederlanden (U.S.)
Capital Corporation, as Agent, and the Lenders named therein. Terms which are
defined in the Agreement are used herein with the meanings given them in the
Agreement. Pursuant to the terms of the Agreement Borrower hereby requests
Lenders to make Advances to Borrower in the aggregate principal amount of
$__________ and specifies ____________, 199__, as the date Borrower desires for
Lenders to make such Advances and to deliver to Borrower the proceeds thereof.

         To induce Lenders to make Advances, Borrower hereby represents,
warrants, acknowledges, and agrees that:

                  (a) The officer of Borrower signing this instrument is the
         duly elected, qualified and acting officer of Borrower as indicated
         below such officer's signature hereto having all necessary authority
         to act for Borrower in making the request herein contained.

                  (b) The representations and warranties of Borrower set forth
         in the Agreement and the other Loan Documents are true and correct on
         and as of the date hereof (except to the extent that the facts on
         which such representations and warranties are based have been changed
         by the transactions contemplated by the Agreement), with the same
         effect as though such representations and warranties had been made on
         and as of the date hereof.

                  (c) There does not exist on the date hereof any condition or
         event which constitutes a Default or Event of Default which has not
         been waived in writing as provided in Section 9.1(a) of the Agreement;
         nor will any such Default or Event of Default exist upon Borrower's
         receipt and application of the Advances requested hereby. Borrower
         will use the Advances hereby requested in compliance with Section 2.3
         of the Agreement.

                  (d) Except to the extent waived in writing as provided in
         Section 9.1(a) of the Agreement, Borrower has performed and complied
         with all agreements and conditions in the Agreement required to be
         performed or complied with by Borrower on or prior to the date hereof,
         and each of the conditions precedent to an Advance contained in the
         Agreement remains satisfied.

                  (e) The Loan Documents have not been modified, amended or
         supplemented by any unwritten representations or promises, by any
         course of dealing, or by any other means not provided for in Section
         9.1(a) of the Agreement. The Agreement and the other Loan Documents
         are hereby ratified, approved, and confirmed in all respects.

                  (f) The outstanding Utilized Credit, after the making of the
         Advances requested hereby, will not be in excess of the Commitment on
         the date requested for the making of such Advances.

         The officer of Borrower signing this instrument hereby certifies that,
to the best of his knowledge after due inquiry, the above representations,
warranties, acknowledgements, and agreements of Borrower are true, correct and
complete.

         IN WITNESS WHEREOF, this instrument is executed as of ____________,
199__.


                                      TPC CORPORATION

                                      By:
                                         --------------------------------------
                                         Name:
                                         Title:








                                       4